Method for metal coating a tubing string in situ in a well



May 28, 1968 T. W. HAMBY, JR. ETAL METHOD FOR METAL COATI NG A TUBINGSTRING IN SITU IN A WELL Filed Sept. 14, 1966 INVENTORS.

TYLER w. HAMBY,JR.

EDWIN A. RICHARDSON ROBERT N. TUTTLE dl-LM THEIR AGENT United StatesPatent ()1 in'ce 3,385,363 Patented May 28, 1968 3,385,363 METHOD FORMETAL COATING A TUBING STRING IN SITU IN A WELL Tyler W. Hamby, Jr.,Edwin A. Richardson, and Robert N. Tuttle, Houston, Tex., assignors toShell Oil Company, N.Y., a corporation of Delaware Filed Sept. 14, 1966,Ser. No. 579,432 Claims. (Cl. 16638) This invention relates to injectionwells for thermally treating a subsurface earth formation and moreparticularly to a method for preventing failure of the casing or acasing-cement bond in an injection oil well.

The producing formations of many oil fields contain low-gravity oilwhose viscosity is of a value sufiiciently high to prevent easy flow ofthe oil from the formation and into a well. In some fields of this type,steam soaking of the producing formation is carried out through one ormore injection wells in order to reduce the viscosity of the productionfluid and drive the heated oil to adjacent wells, in the same field,through which it is produced to the surface.

A typical method for treating an oil-bearing formation by steaminjection is disclosed in US. Patent No. 3,259,- 186 to Dietz. Inmethods of this type an oil well is provided with a casing extendingfrom the top of the well down to at least the top of the producingformation and generally below the producing formation in order to linethe well. Tubing string is mounted concentrically within the casing andthe casing is perforated in the area of the oil-bearing formation topermit steam to escape into the formation. Due to high temperature ofthe steam flowing down the tubing string into the formation radiationheat loss from the tubing string increases the casing temperature. Therise in casing temperature can cause destructive axial thermal stressesto be exerted on the casing. Such operations have resulted in severecasing damage in some injection wells, or rupture or cracking of cementholding the casing in the well. In addition, the heat lost to the casingreduces the available heat introduced into the oil-producing formationand thus reduces the efficiency of the thermal recovery process.Laboratory and field tests have shown that the casing temperature duringsteam injection often exceeds the theoretical maximum allowable casingtemperature and has resulted in casing failures in some thermal wellinstallations. It has been estimated that 90% of the heat transfer fromthe tubing string to the surrounding casing is by radiation.

It is therefore a primary object of the present invention to reduce theradiant heat loss of the tubing string a carrying the steam to theoil-bearing formation.

Another object is to reduce the radiant heat loss by coating the tubingwith a bright reflective material.

Another object of the present invention is to provide a method wherebythe tubing and interior of the well casing are metal-plated in situ.

Still another object of the present invention is to provide a method toincrease the available heat injected into the oil-bearing formation toimprove the thermal recovery process.

These and other objects of the invention will be understood from thefollowing description taken with reference to the drawing whichdiagrammatically illustrates a steam injection well installation incross-section to which the present invention is adaptable.

Referring to the drawing, an injection well casing 10 is cemented in thewell in any suitable manner well known in the art. A tubing string issuspended concentrically within the well casing 10 and extends from thesurface of the earth down to a point in the lower end of the casing 10in the area of an oil-bearing formation 22.

Perforations 16 are provided in the casing 10 which permit theintroduction of steam from the tubing string into the formation.

The top of the well installation is closed in any suitable manner. Forexample, in the arrangement shown, a casing head closure in the form ofa flange 18 is welded to the casing 10 to close the annular space 11between the casing 10 and the tubing string 15'.

It will be readily understood that in the thermal recovery apparatusthus far described, the radiant heat loss from the tubing string 15during steam injection through the tubing string raises the temperatureof the casing 10 an undesirable amount.

In accordance with this invention, the radiation heat loss from thetubing string 15 to the casing 10 can be significantly reduced by brightplating the tubing string with a reflective metallic material therebyreducing the tubing emissivity. It has been discovered that the tubingstring can be effectively plated by contacting the tubing string with:an electroless metal-deposition solution. The electrolessmetal-deposition can be accomplished by contacting the tubing stringwith a metal-deposition solution containing chemicals inclusive of metalions together with a reducing agent which effects a chemical-reductiondeposition of metal on the tubing string. This reaction is carried outunder subsurface well conditions of temperature and pressure.

The metal plating compound can be a polyvalent metal compound of whichthe preferred are nickel, cobalt, copper, iron compounds and mixturesthereof, e.g., nickel and/or cobalt chloride, sulfate and/or nitrate andthese metal compounds are reduced by such reagents as hypophosp-horousacid, hypophosphites, e.g., sodium hypophosphite or alkaline solution ofmolybdenate, formate and/or hydroxy carboxylates, e.g., hydroxyacetate.The concentration of the metal-containing compounds and the reducingagents in aqueous solutions can be varied over a wide range such as from1 to 50%, respectively and preferably from S to 40% each.

To control hydrogen evolution to a minimum as a result of the reaction,the reducing agents in the metalplating solutions should be kept at aminimum generally not in excess of 10% of the total electroless metalplating solution particularly when the solutions are alkaline. Also,hydrogen evolution can be effectively suppressed and the life of themetal-plating reaction increased by addition to such aqueous solutionsbuffering and chelating agents such as hydroxy carboxylic acids andpolycarboxylic acids and their salts, e.g., citric, tartairic, maleic,gluconic, succinic acids or ammonium or alkali metal salts of said acidssuch as sodium citrate, sodium succinate and the like. However, the gascan be effectively eliminated from the area being metalized by applyingpressure of 200 pounds per square inch or more on the system.

When using a hypophosphite as the reducing agent its concentrationshould be controlled since, depending in part on the phosphorous contentof the solution, the metal being deposited can be in the form of analloy of metalphosphorous nickel phosphide. High concentration such asabove 10% of hypophosphite in the metal-plating solution tends to formthese alloys.

Prior to plating the tubing string 15 it is preferable to clean thesurface of the tubing string to remove any paint or foreign material. Asuitable acid or solvent may be injected into the annular space 11through access pipe 12 to accomplish this purpose. One method employedfor contacting the tubing string with either the cleaning agent or themetal-plating compound to be subsequently injected is to till theannular space 11 with the fluid, let it stand and then evacuate theannular space with suitable pumping or pressure means or by openingexpansible packer 14 and draining the fluid into the formation 22.Alternatively, the packer can be left op n and the fluid continuouslyflushed through the annular space 11 thus establishing flowing contactwith the tubing string. The particular type of packer employed is notcritical to the invention since many expansible packers are availableand known in the art which can be remotely opened from the top of thewell to permit draining by retracting the packer away from the casingwall. In some wells, due to the pressure existing in the formation 22,it may be necessary to pressurize the annular space 11 to force thesolutions into the formation.

After the surface of the tubing string has been prepared an aqueoussolution containing one of the above-mention metal-plating compounds andone of the reducing compounds is prepared. The solution is thenintroduced into the well by one of the two methods referred to above,i.e., by filling the annular space 11 or by flushing the solutionthrough the annular space. With either methd, the solution must stay incontact with the tubing string a sutlicient time to permit the metalliccomponent to deposit on the surface of the tubing string. The reactionrate of metal deposition is affected by temperature and for best resultsthe solution should be introduced into the well at a temperature betweenambient and 200 F.; preferably between 100 F. and 190 F.

After contacting for a sufiicient time, the solution is drained into theformation past packer 14 or evacuated by suitable means not shown. Of:course, if the drains 13 are kept open the plating solution iscontinuously drained into formation 22. In addition, gas pressure may besupplied to the upper end of the annular space to drive the solutioninto the formation or back up the inside of the tubing spring 15.

During the procedure thus described, it will be observed that theinterior of the casing will also become metallized as well as any otherferrous surfaces the solution may come into contact with, e.g., theinterior of the tubing string 15. This additional bright coating isdesirable since it further reduces radiant heat loss from the tubingstring to the casing 10. Other arrangements may be employed withoutdeparting from the spirit of the invention. For example, the lower endof the tubing string could be plugged and the string provided with aselectively opened port to place the interior of the tubing string incommunication with the annular space 11. The plating solution could thenbe introduced through the tubing string 15, thus plating the interior ofthe tubing string as well.

In the preferred method described above, it is assumed that the tubingstring is made of steel. if a non-ferrous material is employed, it isnecessary to pretreat the tubing with an activating agent since themetallic component will not deposit on most non-ferrous materials.Palladium-activator solutions or stannous-activator solutions t and/orhydrazine-activator solutions can be used, e.g., a palladium chloridesolution and/or stannous chloride solutions can be used for mixturesthereof.

In addition, when an activator is used and drained into the formation22, the activator will also contact any unconsolidated sand. If theplating solution used to plate the tubing string 15 is subsequentlydrained into the formation. the sand particles become metal-plated toform a permeable, consolidated formation thus preventing collapsing orsloughing of the formation. This result is particularly beneficial sinceit obviates the separate step of consolidating the formation whennecessary, by known methods, e.g., thermally fusing the formation orusing a resinous binder) while at the same time accomplishing theprimary objective of bright coating the tubing string 15 to reduce itsemissivity.

We claim as our invention:

1. A method of bright coating 21 ferrous tubing string within a wellcomprising:

positioning said tubing string within said well;

mixing an aqueous solution of a metal-plating compound and a reducingagent;

introducing into said well said aqueous solution containing saidmetal-plating compound and said reducing agent; and

contacting said tubing string with said solution at We l temperature fora time sutiicient to metal-plate sa d tubing string.

2. The method according to claim 1 including the step of firstcontacting said tubing string with a cleaning solution to remove foreignmaterial therefrom.

3. The method according to claim 1 including the steps of:

lining said well with a ferrous casing; and

contacting the interior surface of said casing with said aqueoussolution at well temperature for a time sulficient to metal-plate saidsurface.

4. The method according to claim 3 including the step providing a packerbetween said casing and said tubing string near the lower end of saidtubing string prior to introducing said solution into said well, wherebya chamber for receiving said solution is formed by said casing, packerand tubing string.

5. The method according to claim 3 wherein:

said metal-plating compound is selected from the group consisting ofinorganic nickel, cobalt, copper and iron compounds.

6. The method according to claim 5 wherein:

said reducing agent is selected from the group consisting ofhypophospherus acid, alkali metal hypophosphite, alkali metalmolybdenate and mixtures thereof.

7. The method according to claim 3 wherein:

said metal-plating compound comprises nickel chloride;

said reducing agent comprises sodium hypophosphite;

and

said aqueous solution is introduced into said well at a temperature of100 F.200 F.

8. A method of bright coating a tubing string within a well comprising:

(a) introducing into said well a first aqueous solution containing anactivating agent;

(-b) contacting said tubing string with said first solution'for a timesufficient to activate the surface of said tubing string to a form thatmay be readily plated by a metal plating compound;

(c) introducing into said well a second aqueous solution containing ametal plating compound and a reducing agent into said well; and

(d) contacting said tubing string with said second aqueous solution fora time sufficient to metal plate said tubing string.

9. The method according to claim 8 wherein:

said activating agent is a compound selected from the group consistingof palladium and stannous chlorides, bromides, nitrates and sulfates andmixtures thereof;

said metal-plating compound is selected from the group consisting ofinorganic nickel, cobalt, copper and iron compounds; and

said reducing agent is selected from the group consisting ofhypophosphorus acid, alkali metal hypophosphite, alkali metalmolybdenate and mixtures thereoff.

10. The method according to claim 8 wherein steps (a) and (c) areperformed simultaneously.

References Cited UNITED STATES PATENTS 1,096,636 3/1914 Mcllroy 204262,084,209 6/1937 Mcilroy l38-l45 3,142,336 7/1964 Doscher 166-11 JAMESA. 'LEPPINK, Primary Examiner.

1. A METHOD OF BRIGHT COATING A FERROUS TUBING STRING WITHIN A WELLCOMPRISING: POSITIONING SAID TUBING STRING WITHIN SAID WELL; MIXING ANAQUEOUS SOLUTION OF A METAL-PLATING COMPOUND AND A REDUCING AGENT;INTRODUCING INTO SAID WELL SAID AQUEOUS SOLUTION CONTAINING SAIDMETAL-PLATING COMPOUND AND SAID REDUCING AGENT; AND CONTACTING SAIDTUBING STRING WITH SAID SOLUTION AT WELL TEMPERATURE FOR A TIMESUFFICIENT TO METAL-PLATE SAID TUBING STRING.